(673b) Trimming Lignin Chemistry for Advanced Manufacturing of Renewable Carbon Fibers

Qiang Li^1,2*, Cheng Hu^1,2, Mengjie Li^1,2, Joshua S. Yuan^1,2*

¹Synthetic and Systems Biology Innovation Hub, Department of Plant Pathology and Microbiology, Texas A&M University, College Station, TX 77843, USA

²Department of Chemical Engineering, Texas A&M University, College Station, TX 77843, USA

*For correspondence: Qiang Li: liqerlee@tamu.edu; Joshua S. Yuan: syuan@tamu.edu

Lignin is a major waste in lignocellulosic biorefinery, where upgrading lignin for fungible value-added products represents one of the most challenging issues. Although lignin has potential for making various materials and chemicals, few commercially viable manufacturing strategies are available for lignin valorization. Recently, lignin has been extensively sought after as carbon fiber precursor due to its high carbon content, renewablility, and low price. However, the quality of current lignin carbon fibers is still too low to be commercialized. In our research, we have revealed that the precursor chemistry regarding lignin chemical heterogeneity including its diverse linkages, molecular weight, and functional groups, rendered the low performance. To overcome lignin heterogeneity, we have developed a series of lignin fractionation, separation and precipitation technologies to trim lignin chemistry. All these technologies enabled lignin-based carbon fibers with much improved mechanical and electro-conductive performance even similar to commercial PAN-based carbon fiber, suggesting potential applications in both auto industry and energy storage devices. Mechanistic study of crystallites in carbon fiber using XRD and Raman microscopy shed light on the mechanism of the improvement. Lignin with more linear structure, uniformity, and intermolecular interactions is critical for the growth of pre-graphitic turbostratic carbon structures in carbon fiber, which determine the mechanical and conductive performances. This research provided a comprehensive analysis on how precursor chemistry impacts lignin-derived carbon fiber performance, and also for the first time synergistically developed lignin carbon fiber with both high mechanical and conductive properties. The technical breakthroughs thus paved the path for making carbon fibers for diverse functions and could guide lignin carbon fiber manufacturing toward commercialization.